Turntables used to support and rotate vinyl records have been available for as long as high fidelity music reproduction has existed. Tone arms are usually of two configurations-those that radially translate along the record surface and those that are pivotally mounted at a fixed location adjacent to the rotating turntable, the latter configuration being the most popular as it generally requires less skill to install and maintains its appropriate operating parameters for an extending period without the need for routine adjustment.
Tone arms are generally supported in a cantilever fashion within a tone arm body which pivots on a vertically extending axis adjacent to the turntable. The tone arm tube supports a shell for receiving a pick up cartridge which, in turn, acts as a receiving body for a stylus. When in use, the stylus fits within a groove created within the vinyl record with the electrical output of the pick up cartridge begin proportional to the lateral displacement of the stylus by the grooved sidewalls. The stylus laterally vibrates within the grooves generally at right angles thereto while moving along a radius measured from the axis of the rotating turntable. Thus, the stylus moves through an arc or path generally at right angles to the grooves created within the vinyl recording. The groove, although being an almost perfect circle is, in fact, in the form of a spiral with its center located at the center of the disk.
In a typical assembly as described above, there are a number of dynamics at play, each of which potentially having a dramatic and profound effect upon the quality of sound reproduction available to a listener. A first critical feature is to properly establish and maintain the appropriate contact pressure between the stylus and the record groove. As noted, the stylus is intended to experience displacement by lateral vibration within the groove sidewalls, generally at right angles thereto. A stylus whose contact pressure is too great or not great enough will experience less than ideal displacement. Adjusting this parameter is generally done with a counterweight cantilevered well behind the pivot point of the tone arm body. Moving the weight closer to this pivot point generally increases the stylus contact pressure while, conversely, moving the weight further behind this pivot point lessens contact pressure. As pick up cartridges of various manufacturers differ dramatically in weight and suggested contact pressures, having the ability to adjust the downward force vector at the pick up cartridge is a necessary characteristic of any modern high quality tone arm assembly. In such an arrangement, however, the tone arm center of gravity is not always aligned with the assembly's bearing point which can attribute to sonic degradation.
Another dynamic which must be accounted for is the need to reduce the tendency of a stylus to “skate” across the record surface. This is because the force exerted on the stylus during playback is at an angle between a line tangent to the groove and a line between the stylus point and the pivot point of the tone arm creating a component of force directed radially inwardly of the record tending to pull the stylus of the center thereof. Conventionally, counterweights are hung at various positions proximate the tone arm body to exert forces tending to counter skating. However, as the skating forces vary depending upon the position of the stylus along the record surface, traditional anti-skating mechanisms create forces that may only be ideal at a certain stylus location but not when the stylus is located elsewhere.
Other considerations beyond those described above can be equally important. Specifically, the appropriate tone arm/turntable set up requires establishing the appropriate vertical tracking angle (VTA) which is the stylus rake angle between the stylus and groove This angle is normally adjustable by raising or lowering the tone arm body and is generally considered appropriate or “neutral” when the tone arm tube is parallel to the record surface.
Another parameter requiring some consideration is the azimuth. Looking at the cartridge body from its front, the angle of the stylus to the record surface should be perpendicular.
One most also consider the zenith and the amount of overhang between the stylus and shell to ensure that the stylus remains tangent to the record groove. Setting overhang amounts to aligning the cartridge so that the stylus can follow an ideal arc across the record although, when properly set, there are only several points (null points) when this actually occurs. Various gauges are available from tone arm manufacturers and third party suppliers for assisting a user in establishing the proper overhang.
Although great advances have been made in turntable design, standard counterweight assemblies fail to maintain the tone arm center of gravity at or near the tone arm bearing point which is an area requiring improvement to which the present invention is intended to address. Further, an anti-skate mechanism which improves the quality of forces experienced by the stylus along the record surface is another area improved upon by the present invention. Finally, the present disclosure suggests a modification in the standard pick up cartridge shell located at the end of the tone arm tube makes the job of establishing appropriate overhang much easier than in the past.
These and further improvements will become readily apparent when considering the following disclosure and appended claims.